The secret of living to 100

By Dr. Sanjay Gupta CNN

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(CNN) -- Dr. Thomas Perls is a leading expert on aging, so I was a little nervous when he arrived recently at my house at 6:20 a.m. He was there to assess how the daily decisions I'm making are affecting my life expectancy.

Minutes into our walk with Bosco, my Weimaraner, I was in trouble. Perls asked me how much sleep I'd gotten the night before. Perls has a Web site called www.livingto100.com, which has a detailed life expectancy calculator. The calculator factors lifestyle, nutrition and family history to come up with an estimate of how long you'll live.

I had to admit I'd been in surgery until 1 a.m. and had only slept for four hours. Routinely not getting enough sleep subtracts 1 year from your life expectancy, according to Perls. Fortunately, I usually sleep more than four hours, and when I do sleep, I'm dead to the world.

Dr. Perls liked my morning habit of walking Bosco. Even though he viewed the daily walk as a stress reliever, he considered my dual life as neurosurgeon and television correspondent as stressful. Subtract two years of life expectancy. Cutting back my work schedule to five days a week, instead of six, could add 1.5 years to my life.

During breakfast, Dr. Perls quizzed me about the frozen omelet I was eating. It was packed with protein, but a little too much fat for his liking. He also wanted to know how much I was eating at other meals. The well-known gerontologist told me I should be able to cover my meals with my hand.

Dr. Perls was pleased to see me brush and floss after breakfast. I didn't realize that flossing not only helps prevent gum disease but heart disease as well. Add 1 year.

I run about three times a week. Add three years. Still, if I exercised every day, I could add five more years to my life expectancy, according to the calculator.

Weight training is especially important, according to Dr. Perls. The goal should be "really building muscle because we really start to be so prone to losing muscle, and that is such an important part of slowing down aging and decreasing the risk for age-related diseases. So much seems to boil down to having muscle on board," Perls said.

Lifting weights helps maintain bone density and also lessens the risk of falls, which can have catastrophic consequences in the elderly.

Dr. Perls followed me into CNN Center. After an appearance on "American Morning," I rejoined Dr. Perls to talk some more about my family history of heart disease and diabetes. From there, I checked on patients at Grady Hospital where I'm a neurosurgeon -- stopped home briefly -- then drove to the airport to catch an afternoon flight to Los Angeles, California, for a late-breaking story.

As I picked up my boarding pass, Dr. Perls gave me the verdict: according to his calculator, my life expectancy is 81 years. Not bad, but I was disappointed. My family history was probably the biggest thing dragging me down along with my 80-hour workweeks. But I took solace in knowing that if I improve my habits now, I can certainly add years to my life expectancy. So can you.